The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

Abstract

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been
widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma
irradiation has been successfully employed in the modification/sterilization of such porous
composites and that it has advantages over other procedures. In this study, differential scanning
calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass
transition behavior and structural relaxation, as well as to estimate the activation energy for this
process. The apparent activation energy ΔH* for structural relaxation in the glass transition region
was determined on the basis of the heating rate dependence of the glass transition temperature Tg.
Furthermore, the results were correlated with those obtained by gel permeation chromatography
(GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is
the main reason for the decrease of the glass transition temperature and/or activation energy with
the absorbed dose.